The present invention relates in general to a speaker system, and more particularly, to a speaker system employing a passive radiator for enhancing the low frequency response of the system.
The passive radiator has been employed in the art to extend the low frequency response of the low frequency drivers (woofers) of speaker systems. Originally, these devices were known as drone cone radiators. The passive radiator is many times constructed in the same way as a conventional speaker except for the omission of the magnet and voice coil. The mass of the cone, the radiation inertia, and the stiffness of the suspension system form a resonant system which interacts with the active driver by coupling through the enclosed air of the speaker cabinet or enclosure and also the air directly in front of the speakers. The system employing a passive radiator is designed in a way approximately the same as is used in base reflex or Helmholtz resonator speaker systems. In such systems it is typical for the passive radiator to be mounted on the front panel of the speaker enclosure in the same plane, next to but below the low frequency driver (woofer). The placement of the woofer above the passive radiator essentially elevates the woofer to an undesirable position as far as uniform loading is concerned. Also, this particular forward facing position of the passive radiator allows for re-radiation of internal reflections.
In the past, some conventional acoustic suspension systems, designed without a passive radiator, have had the woofer or woofers disposed in the lowermost position of the speaker enclosure for improved loading. In at least one case the woofer has been positioned at the bottom of the cabinet facing downward. In some systems a stand is provided to raise the enclosure a distance above the floor to enhance the sound communication. Such systems have proven to be unsatisfactory at least in some regard. When the woofer is disposed in its lowermost position close to the floor, the upper base or mid-range information is not readily radiated, whereas, on the other hand, with the woofer raised considerably above the floor, there tends to be sound interference effects generated.
Accordingly, it is an object of the present invention to provide an improved speaker system employing a passive radiator which enhances the communication of low frequency sounds but without the attendant problems outlined hereinabove.
Another object of the present invention is to provide an improved speaker system employing a passive radiator causing an attenuation of the radiation of upper base and mid-range internal reflections.
Still another object of the present invention is to provide an improved speaker system employing a passive radiator that may be of smaller size than in conventional systems.
A further object of the present invention is to provide an improved speaker system employing a passive radiator and which is also characterized by uniform loading.